Answer
$62cm, 62cm, 25cm $
Work Step by Step
Let the equal side of an isosceles triangle be $x$ and unequal side is $y$
Equal side is twice the length of the unequal side and increased by $12$ cm
$x=2y+12$
Perimeter of an isosceles triangle is $149$ centimeters.
$x+x+y=149$
$2y+12+2y+12+y=149$
$5y+24=149$
$5y=149-24$
$5y=125$
$y=25$
Equal side : $ x = 2y+12 = 2(25)+12 = 50+12 = 62 $ cm
Unequal side :$y=25$ cm
Three sides of pennant are $62cm, 62cm, 25cm $